Method and apparatus for determination of object topology

Abstract

Electronic devices may include imaging systems with camera modules and light sources. A camera module may be used to capture images while operating one or more light sources. Operating the light sources may generate changing illumination patterns on surfaces of objects to be imaged. Images of an object may be captured under one or more different illumination conditions generated using the light sources. Shadow patterns in the captured images may change from one image captured under one illumination condition to another image captured under a different illumination condition. The electronic device may detect changes in the shadow patterns between multiple captured images. The detected changes in shadow patterns may be used to determine whether an object in an image is a planar object or an object having protruding features. A user authentication system in the device may permit or deny access to the device based, in part, on that determination.

What is claimed is: 
     
         1 . A method for authenticating a user of an electronic device having a camera module and a light source, comprising:
 with the camera module, capturing a first image of the user;   operating the light source;   with the camera module, while operating the light source, capturing a second image of the user; and   determining whether the user is an authorized user using the first image and the second image.   
     
     
         2 . The method defined in  claim 1  wherein determining whether the user is an authorized user using the first image and the second image comprises:
 extracting shaded portions of the first image; 
 extracting shaded portions of the second image; and 
 determining whether the shaded portions of the first image are different from the shaded portions of the second image. 
 
     
     
         3 . The method defined in  claim 2 , further comprising:
 in response to determining that the shaded portions of the first image are different from the shaded portions of the second image, performing facial recognition operations.   
     
     
         4 . The method defined in  claim 3  wherein performing the facial recognition operations comprises:
 determining whether a face in the first image of the user is the face of an authorized user of the device. 
 
     
     
         5 . The method defined in  claim 4  wherein determining whether the face in the first image of the user is the face of the authorized user of the device comprises:
 accessing facial information associated with authorized users of the device that is stored in the electronic device; and 
 comparing the face in the first image to the accessed facial information. 
 
     
     
         6 . The method defined in  claim 2 , further comprising:
 in response to determining that the shaded portions of the first image are not different from the shaded portions of the second image, providing a security verification failure notification.   
     
     
         7 . The method defined in  claim 6  wherein the electronic device includes a display and wherein providing the security verification failure notification comprises providing the security verification failure notification using the display. 
     
     
         8 . The method defined in  claim 2  wherein the light source includes a display and wherein operating the light source comprises:
 activating a first portion of the display; and 
 while activating the first portion of the display, inactivating a second portion of the display. 
 
     
     
         9 . The method defined in  claim 2  wherein the electronic device includes an additional light source, the method further comprising:
 operating the additional light source; and 
 with the camera module, while operating the additional light source, capturing a third image of the user, wherein determining whether the user is the authorized user using the first image and the second image comprises determining whether the user is the authorized user using the first image, the second image, and the third image. 
 
     
     
         10 . A method for generating a depth image of a scene using an electronic device having an image sensor and a light source, comprising:
 capturing a first image of the scene using the image sensor;   illuminating the scene using the light source;   capturing a second image of the scene using the image sensor while illuminating the scene using the light source;   extracting shadow information from the first image and shadow information from the second image;   comparing the shadow information from the first image with the shadow information from the second image; and   extracting depth information associated with distances to surfaces of objects in the scene using the comparison of the shadow information from the first image with the shadow information from the second image.   
     
     
         11 . The method defined in  claim 10 , further comprising:
 illuminating the scene using an additional light source; and   capturing a third image of the scene using the image sensor while illuminating the scene using the additional light source.   
     
     
         12 . The method defined in  claim 11 , further comprising:
 extracting shadow information from the third image.   
     
     
         13 . The method defined in  claim 12 , further comprising:
 comparing the shadow information from the third image with the shadow information from the first image and the shadow information from the second image; and   extracting additional depth information associated with the distances to the surfaces of the objects in the scene using the comparison of the shadow information from the third image with the shadow information from the first image and the shadow information from the second image.   
     
     
         14 . The method defined in  claim 13 , further comprising:
 generating the depth map using the extracted depth information and the extracted additional depth information.   
     
     
         15 . A facial recognition security verification system, comprising;
 a housing having a bezel portion;   a camera module mounted in the bezel portion;   a plurality of light sources; and   control circuitry for operating the camera module and the plurality light sources, wherein the control circuitry is configured to operate the plurality of light sources to generate changing shadow distributions on a face and to capture a plurality of images of the face while generating the changing shadow distributions on the face and wherein the control circuitry is configured to determine whether the face in the captured plurality of images is a planar object or an object having protruding features using the plurality of images that were captured while generating the changing shadow distributions on the face.   
     
     
         16 . The security system defined in  claim 15  wherein the plurality of light sources comprise:
 a display; and 
 an additional light source mounted in the bezel portion of the housing. 
 
     
     
         17 . The security system defined in  claim 15  wherein the plurality of light sources comprises first and second light sources mounted in the bezel portion of the housing. 
     
     
         18 . The security system defined in  claim 17  wherein the first and second light sources comprise first and second light-emitting diodes. 
     
     
         19 . The security system defined in  claim 15  wherein the plurality of light sources comprises at least first and second portions of a display and wherein the control circuitry is configured to operate the camera module and the first and second portions of the display to capture a first image while operating the first portion of the display and to capture a second image while operating the second portion of the display. 
     
     
         20 . The security system defined in  claim 15  wherein the plurality of light sources comprises at least one light source configured to emit near-infrared light and wherein the camera module comprises at least one image sensor configured to receive near-infrared light.